Rate Matters (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2021	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Fuel Rules [Abstract]
Deferred fuel rules monitored costs	$ 0.5				$ 3.2	$ 1.5
Rate Matters For Future Periods [Member] | Subsequent Event [Member]
Rate Proceedings [Abstract]
Proposed return on equity, percentage			9.80%
Proposed equity capital structure, percentage			55.60%
PSCW [Member] | MGE [Member]
Rate Proceedings [Abstract]
Authorized return on equity, percentage	9.80%				9.80%	9.80%
Approved equity capital structure, percentage	55.80%				56.10%	56.60%
Fuel Rules [Abstract]
Fuel rules, bandwidth	1.00%				2.00%
Fuel rules, electric fuel deferred costs upper threshold	101.00%
Fuel rules, electric fuel deferred costs lower threshold	99.00%
Electric Rate Proceeding [Member] | Rate Matters For Future Periods [Member] | Subsequent Event [Member]
Rate Proceedings [Abstract]
Proposed rate increase (decrease), percentage			5.90%
Electric Rate Proceeding [Member] | PSCW [Member] | MGE [Member]
Rate Proceedings [Abstract]
Authorized rate increase (decrease), percentage	0.00%				(0.84%)	(2.24%)
Authorized rate increase (decrease), amount					$ (3.4)	$ (9.2)
Electric Rate Proceeding [Member] | PSCW [Member] | Rate Matters For Future Periods [Member] | MGE [Member]
Effects Of The Tax Cuts And Jobs Act [Abstract]
Return of unprotected excess deferred taxes				$ 18.2
Gas Rate Proceeding [Member] | Rate Matters For Future Periods [Member] | Subsequent Event [Member]
Rate Proceedings [Abstract]
Proposed rate increase (decrease), percentage		1.65%	3.00%
Gas Rate Proceeding [Member] | PSCW [Member] | MGE [Member]
Rate Proceedings [Abstract]
Authorized rate increase (decrease), percentage	4.00%				1.46%	1.06%
Authorized rate increase (decrease), amount					$ 2.4	$ 1.7